Certain oxazolo benzothiazole compounds and process



= Patented fusion of a 6-alkoxy substituted benzothiazole as described in Clark, Doorenbos and Horwitz U. S. appli- 2,375,231 cation, Serial Number 633,198, filed on January 9, 1957 is converted by treatment with an acid anhydride, e. g., acetic g ggg gggg g gw 5 anhydride, propionic anhydride, butyric anhydride, or an acyl halide, e. g., acetyl chloride, propionyl chloride, phen- Les'tef HOI'WilZ, Alballsi Y! assign)! to General ylacetyl chloride, phenylpropionyl chloride to a 6-acyloxy- Aniline Film cmporafion New York a benzothiazole which is substituted in the 2-position by an potato 0f Delaware aralkyl or alkyl group. Hydrolysis or saponification of N0 Dl'aWing- Application F y 1957 10 the 6-acyloxybenzothiabole with dilute alkali, e. g., sodium serial 641,875 hydroxide leads to the 6-hydroxy-2-alkyl-(or -2 aralkyl) 8 Claims. (Cl. 260-304) benzothiazole (I) which is converted by coupling with a diazonium salt such as phenyldiazonium chloride or another suitable aryldiazonium chloride into 2-alkyl-(or This invention relates to 2,6-disubstituted oxazolo- 1 5 aralkyl) -P Y Y Y [4,5-f]benzothiazole and more particularly to Z-methyl- Reductlon Wlth scldmm hydrqsulfite m alkaline q m oxazolo[4,5-flbenzothiazoles which are substituted in the leads the Y ly y f f fi-position b an lk l, l or lk l group; h quater. (HI). Finally, refluxing the latter with an acid anhydrlde nary salts thereof, sensitizing dyes d i d th f or with an acyl halide, followed by successive distillaand silver halide emulsions sensitized with such dyes. t on f t e ce anhydride and of the reaction P o Diazole radicals such as benzobisthiazoles have already yields the 2,6 -disubstituted oxazolo [4,5-flbenzoth1azole been recommended as intermediates in the preparation of (IV). These reactions are illustrated by the following certain cyanine dyes. However, the synthetic methods formulae.

8 ArNi Y HO New.

L NZC-R ArN= \N/ -R III IV H0 (Bloom Distillation L I HQN \N//CR Rr- \N \N//C-R described so far provide only diazole nuclei in which wherein R and R have the values given above, Ar is the the azole nuclei attached to the benzene moiety are aryl residue of the diazonium salt and Y is an anion identical. such as chloride, bromide, sulfate and the like.

I have now found that extremely valuable sensitizing The above obtained oxazolobenzothiazole base may be dyes may be prepared from oxazolo[4,5-f] benzothiazoles readily quaternized by conventional methods to produce which contain alkyl or aralkyl groups in the 2-position 40 the desired cyclammonium quaternary salts for the and alkyl, aryl or aralkyl groups in the 6-position. These cyanine dye synthesis; for instance, the methiodide or bases, which are readily quaternized by conventional ethiodide is obtained by heating the base with methyl or methods, can be reacted with cyclammonium quaternary ethyl iodide under pressure in a sealed container for sevsalts containing a reactive group on the u-carbon to proeral hours at 96-100 C. The quaternary salts obtained duce inter alia, monoand poly-methine cyanine dyes are characterized by the following general formula: which are valuable sensitizers for silver halide emulsions.

Among the objects of my invention are said bases, their O s preparation, quaternary salts derived therefrom, sensi tizing dyes produced with said quaternary salts, and silver Rr- R halide emulsions sensitized with said dyes. \\N/ \N/ The new bases, the preparation and use of which are R1 X contemplated herein, are 2,6-disubstituted oxazolo[4,5-'f] h i R and R have the values given above, R is benzoihialoles having the following strucml'ci alkyl such as methyl, ethyl, propyl, ,B-hydroXyethyL'yhydroxypropyl, carboxymethyl, carboxyethyl, and the 0 8 like; aralkyl, e. g., benzyl, phenethyl and the like, and X y 1 is an anion such as chloride, bromide, iodide, perchlorate Rr- Q5 ago-R p-toluenesulfonate and the like.

N The above quaternary ammonium salts may be conwherein R is alkyl such as methyl, ethyl, propyl, butyl verted to sensitizing dyes characterized by the following and the like; aralkyl such as benzyl, phenethyl and the general formula: v 0 s I A R1C\ /C=C H(H=C H) Pi-C H CH) m-1=N\ N I x like; R is alkyl such as methyl, ethyl, propyl, butyl and wherein R and R have the values given above, n reprethe like; aryl such'as phenyl, tolyl, xylyl and the like; ,sents a positive integer of from 1 to 4; m represents a aralkyl such as benzyl, phenethyl and the like. positive integer of from 1 to 2; A represents hydrogen or These compounds are prepared as follows: a lower alkyl group such asmethyl, ethyl and the like; R; Z-amino-S-hydroxybenzenethiol prepared by the alkali a 7 represents an alkyl group such as methyl, ethy l, propyl,

bntyl, mm; a hydroxyalkyl grou such as hydroxymethyl,

necessary to complete a 5- or 6-men'1bered nitrogenous heterocyclic system of the type used in cyanine dyes, such as pyridine, lepidine, quinoline, indoline, oxazole, thiazoline, thiazole, selenazole, selenazoline, oxazoline, benzothiazole, benzoselenazole, benzoxazole, naphthothiazole, and the like.

These sensitizing dyes are prepared by heating the above oxazolobenz'othiazolium salts in the presence of an acid binding agent such as pyridine, trimethylamine, triethylamine, and the like with a cyclammonium quaternary salt having a reactive grouping on the carbon atom in the 2-position of the heterocyclic ring such as a halogen atom, e. g., chlorine, bromine or the like; an alkyl mercapto group, e. g., methylmcrcapto, ethylmercapto and the like; an alkylmercaptovinyl group, e. g., S-methylmercaptovinyl, fl-ethylmercaptovinyl and the like, B-alkylmercapto-fl-alkylvinyl, e. g., fi-methylmercapto-fi-methylvinyl, fl-ethylrnercapto-fi-ethylvinyl and the like; B-acetanilidovinyl, 4-acetanilido-1,3-butadienyl, and 6-acetanilido-1,3,5-hexatrieny1.

As examples of suitable cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the 2-position to the nitrogen atom thereof so as to form a monomethine dye, the following may be mentioned:

2-methylmercapto-6-methylquinoline ethiodide 2-methylmercaptopyridine ethiodide Z-methymercaptothiazoline ethiodide Z-phenylmercaptothiazoline ethiodide, and the like In preparing trimethine cyanine dye salts, the following cyclamrnon-ium quaternary dye salt intermediates hav- .ing a reactive group in the B-position of the side chain in the 2-position of the nitrogen atom thereof may be employed;

2- (fi-acetanilidovinyl thiazoline ethiodide Z-(B-acetanilidovinyl)benzothiazole ethiodide '2-.(;9-acetanilidovinyl) benzoxazole ethiodide 2 (pl-ethyl-fi-methylmercaptophenyl) 5 methoxybenzoselenazole ethiodide 2 (,B-methylmercapto [3 methylvinyl)benzothiazole eth iodide 2 (pz-methylrnercapto propylvinyl)benzothiazole ethiodide In preparing pentamethine and heptamethine cyanine dyes, the following cyclammonium quaternary salts having a reactive group in deltaand zeta-positions of the side chain in 2-position of the nitrogen atom thereof may be employed.

2-(4-acetanilido-1,3-butadienyl)pyridine ethiodide 2-(4-acetanilido-1,3-butadienyl)benzoxazole ethiodide 2-(4-anilino-3-methyl-l,3-butadienyl)pyridine ethiodide .2,-. (4-anilino-3-methyl 1,3 butadienyl)-,B-naphthoxazole 4 butyl 1,3,5 hexatrienyl)benzothiazole The new dyes of my invention have been found to be particularly useful since they operate to increase the sensitivity of photographic emulsions containing color formers fast to diifusion to a higher extent than comparable sensitizing dyes Without the oxazolobenzothiazole nucleus. The sensitizing bands of the new dyes of my invention are unusually sharp so that they render themselves advantageously for use in color emulsions.

The invention is further illustrated by the following examples although it is to be understood that the invention is not to be restricted thereto.

PREPARATION OF INTERMEDIATES v Example I.--2-methyl-5-phenyldiazo-6- hydroxybenzothiazole C--CH:

. lated by filtration and allowed to dry. Yield 93%.

Example II.--2-methyl-5-amin0-6-hydr0xybenz0thiazole The product prepared according to Example I was dissolved in a solution prepared from 20 grams of sodium hydroxide and 165 mls. of water. The reaction mixture was heated to 95 C. on the steam bath and 42 grams of sodium hydrosulfite was added. Stirring Was continued for 10 minutes after the addition. The reaction mixture was cooled to room temperature and then extracted with ether. The aqueous layer was rendered neutral by the addition of acetic acid; the product which precipitated out was collected and dried; yield 11.95 grams. Recrystallization from a methanol-water mixture gave a pure product melting with decomposition at 193 C.

; Example III.-2,6-dimethyl0xaz0lo[4,5-1]benzothiazole CHr-C U C-GHI pump at a pressure of 3-4 mm. The yellow oil which came over between -170 C. solidified upon cooling. Recrystallization from acetonitrile provided a pure product melting at 270 C. Yield 8.7 grams.

Example I V.-2,3,6-trimethyloxazole[4,5-flbenzothiazolium iodide Two grams of the produ'ctof Example 111 and 7 mls. Example X.-'3-carboxyethyl-3'-ethyl-6-methoxy 5,6- of methyl iodide were heated in a bomb on the steam [2-methyl0xazolo 4,5]2hiapseud0cyanine iodide bath for hours. The resulting quaternary salt was purified by washing with ether; M. P. 2ss.s C. 7 Example V.3-ethyl-2,6-dimethyloxazolo[4,5-f1- 5 CHa-C C=CH benzothiazolium iodide N Two grams of the product of Example III and 5 mls. N f lzHi of ethyl iodide were heated in a sealed container for 6 U hours at 9640M C. -10 T1118 dye was prepared from 0.37 gram (0.001 mole) of 3 carboxyethyl 2,6 dimethy1oxazolo[4,5 flbenzo- Example VI.3-carboxymethyl-2,6-dimethyloxaz0l0- thiazolium iodide, and 0.38 gram (0.001 mole) of l-ethyl- [4,5-flbenzothiazolium bromide Z-ethylmercapto-6-methoxyquinolinium iodide using the T w 0 grams of the product of Example In and 175 method described in Example VIII. The resultant dye grams of bromoacetic acid were fused together in a sealed had an absorption maxlmum at 487 container at 140? C. for 4 hours. The resulting product Example XI.3,9-diethyl-5-meth0xy-3'-methyl-5',6- [2- was triturated with ether and acetone, filtered and dried. methyloxazolo 4,5 Jselenathiacarboxyanine iodide -0CH| i C211: 1'' Example VII.3-carbo xyethyl-2,6,dimethyloxaz0lo- A mixture of 0.346 gram (0.001 mole) of 2,3,6-tri- [4,5-f1benz0thiazolium iodide methyloxazolo[4,5-f1benzothiazo1ium iodide, 0.47 gram 0.001 mole) of 2-(13-methylmercapto)-buteny1-(1)-5- Two grams of the product of Example III and 2.2 r

grams of iodopropionic acid were heated together in a a fgz i i ig h of smetpanol sealed container at 135 C. for 3 hours. The resulting i an g 3 3. eats g g product was purified by washing with ether and dried. on a m a 6 ye 16 separate 9 coo g was purified with methanol, absorption maximum 558 PREPARATION OF DYES i E l th th th I l Example XII.-4,5-benz0-3,9-diethyl-3 -methyl-5',6f-[2- xamp e -i gg i i y 0mm 0 methyloxazolo 4,5]thiacarbocyanine iodide 2115 CH: 1 I V A mixture of 0.346 gram 0.001 mole) of 2,3,6-tri- 4 This ye p p from 035 gram 1 mole) methyloxazoloE4,5-f1benzothiazolium iodide,'0.345 gram of 2,3,6-tf1methYl0XaZ010[4,5-flbe11Z0thiaZ0l1um dide (0.001 mole) of 1-ethy1-2-ethy1mercaptoquinolinium iovand gram 111016) of -(fip dide, 5 mls. of methanol and 10 drops of triethylamine y Y Od de essenwas heated and kept at boiling for 5 minutes. The resulttifllly described in Example The absorption maxiant dye was filtered off and purified by boiling with mum 111 alcohol was 560 l methanol. It had an absorptlon maximum of 484 m m l methyloxazola 4,5 Jthiacarbocyanine iodide Example IX.-3,1-diethyl-6-methoxy-5,6-IZ-methyloxazolo 4,5] thiapseudocyanine iodide o 8 0,115

GHI-C/ C=CH-( JCH-C /o s\ 0 cm N/ C=CH c H H N z a v a s I? I H 50 1 2 5 This dye was prepared from 0.36 gram (0.001 mole) of 2,6-dimethyl-3-ethyloxazolo[4,5-f]benzothiazolium io- This dye was prepared from 0.35 gram (0.001 mole) dide and 0.43 gram (0.001 mole) of 2-(fi-methylmercapof 2,6-dimethy1-3-ethyloxazolo[4,5-f1benzothiazolium iotObutenyl-(l))-3-methyl-4,S-benzothiazolium iodide esdide and 0.38 gram 0.001 mole) of 1-ethyl-2-ethy1mere5 senti ally as described in Example XIL The absorption capto-6-methoxyquinoliniurn iodide according to the promaxlmum ethanol was 563 lcedllfe described in x p The absorption maxi- Example XI V.3'-carboxyetl1yl-3,9-diethyl-5-meth0xy-5 CHs-C mum in ethanol was 495 mp. 6-[2-mezhyloxazolo 4,5] selenathiacarbocyanine iodide /O S\ C H Se 2 5 GHs-C C=CH-=OH-O N/ oorn ample.

Example X V.-4,5-benz-3'-carboxyethyl-9-ethyl-5-meth- 'yl-S',6'-[2-methyl0xazolo 4,5]thiacarbocyanine iodide I l omcmooon on;

. I" The above dye was synthesized from 0.37 gram (0.001

, mole) of 3-carboxyethyl-2,G-dimethyloxazolo[4,5-f] benzothiazolium iodide and 0.43 gram (0.001 mole) of 2-(5- methylmercapto) butenyl-( 1 )-'3-methyl-4,5-benzobenzothiazolium iodide as described in Example XII. The absorption maximum in ethanol was 565 m Many variations of my invention will occur to persons skilled in the art. For instance, in the synthesis of the S-aryldiazo-6-hydroxybenzothiazole which serves as an intermediate for the preparation of the oxazolobenzothiazole, other diazonium salts may be used in place of the phenyldiazonium chloride illustrated by the ex- The use of oxazolobenzothiazole nuclei which are substituted in the 2-position by a benzyl group leads to carbocyanines which carry a benzene nucleus assubstituent of the trimethine chain in the a-position. The

use 0t oxazolobenzothiazoles, which are substituted in the 6-position by aralkyl or aryl groups or by alkyl groups other than the illustrated methyl group leads to dyes which contain the corresponding substituent in the 6- position of the oxazolobenzothiazole nucleus. I, therefore, do not intend to be limited in the patent granted" except as necessitated by the appended claims.

Iclaim:

- 1. A process of preparing 2,6-dimethyloxazolo[4,5-f] benzothiazole which comprises coupling 6-hydroxy-2- methylbenzothiazole with an aryl diazonium salt, reducing the resulting 6-hydroxy-2-methyl-5-ary1 diazobenzothiazole in an alkaline medium to form the S-amino- 6-hydroxy-2-methylbenzothiazole, acetylating the latter with an excess of acetic anhydride, removing the excess of acetic anhydride, and effecting closure of the oxazole ring by heating the acylated product to its boiling point under reduced pressure.

2. A process'of preparing 2,6-dimethyloxazolo[4,S-f] benzothiazole which comprises coupling 6-hydroxy-2- methylbenzothiazole with a phenyldiazonium salt, reducing the resulting 6-hydroxy-2-methyl-S-phenyldiaiobenzothiazole in an alkaline. medium to form the S-amino- 6-hydroxy-2-methylbenzothiazole, acetylating the latter with an excess of acetic anhydride, removing the excess of acetic anhydride, and efiecting closure of the oxazole ring by heating the acylated product to its boiling point under reduced pressure.

3. Sensitizing dye intermediates selected from the group consisting of the compounds having the following general formulae:

wherein R is selected from the class consisting of methyl, ethyl, propyl and butyl, R is selected from the class consisting of methyl, ethyl, propyl and butyl, R is a member selected from the class consisting of methyl, ethyl, propyl, -hydroxyethyl, -hydroxypropyl, carboxymethyl and carboxyethyl and wherein X is an anion.

4. A sensitizing dye intermediate having the following formula:

5. 2,3,6-trimethyloxazolo 4,5-f benzothiazolium iodide.

6. 3-ethyl-2,6-dimethyloxazolo 4,5-f benzothiazolium iodide.

7. 3-carboxymethyl-2,6-dimethy1oxazolo 4,5-f benzothiazolium bromide.

8. 3-carboxyethyl-2,6-dimethyloxazolo 4,5-f benzothiazolium iodide.

References Cited in the tile of this patent Elderfield: Heterocyclic Compounds, vol. 5, pages 420-4 (1957). 

3. SENSITIZING DYE INTERMEDIATES SELECTED FROM THE GROUP CONSISTING OF THE COMPOUNDS HAVING THE FOLLOWING GENERAL FORMULAE: 